forked from rust-lang/rust
-
Notifications
You must be signed in to change notification settings - Fork 1
/
Copy pathexpr.rs
2182 lines (2010 loc) · 86.3 KB
/
expr.rs
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
use std::assert_matches::assert_matches;
use super::errors::{
AsyncCoroutinesNotSupported, AwaitOnlyInAsyncFnAndBlocks, BaseExpressionDoubleDot,
ClosureCannotBeStatic, CoroutineTooManyParameters,
FunctionalRecordUpdateDestructuringAssignment, InclusiveRangeWithNoEnd, MatchArmWithNoBody,
NeverPatternWithBody, NeverPatternWithGuard, UnderscoreExprLhsAssign,
};
use super::ResolverAstLoweringExt;
use super::{ImplTraitContext, LoweringContext, ParamMode, ParenthesizedGenericArgs};
use crate::errors::YieldInClosure;
use crate::{FnDeclKind, ImplTraitPosition};
use rustc_ast::ptr::P as AstP;
use rustc_ast::*;
use rustc_data_structures::stack::ensure_sufficient_stack;
use rustc_hir as hir;
use rustc_hir::def::{DefKind, Res};
use rustc_hir::HirId;
use rustc_middle::span_bug;
use rustc_session::errors::report_lit_error;
use rustc_span::source_map::{respan, Spanned};
use rustc_span::symbol::{kw, sym, Ident, Symbol};
use rustc_span::DUMMY_SP;
use rustc_span::{DesugaringKind, Span};
use thin_vec::{thin_vec, ThinVec};
impl<'hir> LoweringContext<'_, 'hir> {
fn lower_exprs(&mut self, exprs: &[AstP<Expr>]) -> &'hir [hir::Expr<'hir>] {
self.arena.alloc_from_iter(exprs.iter().map(|x| self.lower_expr_mut(x)))
}
pub(super) fn lower_expr(&mut self, e: &Expr) -> &'hir hir::Expr<'hir> {
self.arena.alloc(self.lower_expr_mut(e))
}
pub(super) fn lower_expr_mut(&mut self, e: &Expr) -> hir::Expr<'hir> {
ensure_sufficient_stack(|| {
match &e.kind {
// Parenthesis expression does not have a HirId and is handled specially.
ExprKind::Paren(ex) => {
let mut ex = self.lower_expr_mut(ex);
// Include parens in span, but only if it is a super-span.
if e.span.contains(ex.span) {
ex.span = self.lower_span(e.span);
}
// Merge attributes into the inner expression.
if !e.attrs.is_empty() {
let old_attrs = self.attrs.get(&ex.hir_id.local_id).copied().unwrap_or(&[]);
self.attrs.insert(
ex.hir_id.local_id,
&*self.arena.alloc_from_iter(
e.attrs
.iter()
.map(|a| self.lower_attr(a))
.chain(old_attrs.iter().cloned()),
),
);
}
return ex;
}
// Desugar `ExprForLoop`
// from: `[opt_ident]: for await? <pat> in <iter> <body>`
//
// This also needs special handling because the HirId of the returned `hir::Expr` will not
// correspond to the `e.id`, so `lower_expr_for` handles attribute lowering itself.
ExprKind::ForLoop { pat, iter, body, label, kind } => {
return self.lower_expr_for(e, pat, iter, body, *label, *kind);
}
_ => (),
}
let hir_id = self.lower_node_id(e.id);
self.lower_attrs(hir_id, &e.attrs);
let kind = match &e.kind {
ExprKind::Array(exprs) => hir::ExprKind::Array(self.lower_exprs(exprs)),
ExprKind::ConstBlock(c) => {
let c = self.with_new_scopes(c.value.span, |this| hir::ConstBlock {
def_id: this.local_def_id(c.id),
hir_id: this.lower_node_id(c.id),
body: this.lower_const_body(c.value.span, Some(&c.value)),
});
hir::ExprKind::ConstBlock(c)
}
ExprKind::Repeat(expr, count) => {
let expr = self.lower_expr(expr);
let count = self.lower_array_length(count);
hir::ExprKind::Repeat(expr, count)
}
ExprKind::Tup(elts) => hir::ExprKind::Tup(self.lower_exprs(elts)),
ExprKind::Call(f, args) => {
if let Some(legacy_args) = self.resolver.legacy_const_generic_args(f) {
self.lower_legacy_const_generics((**f).clone(), args.clone(), &legacy_args)
} else {
let f = self.lower_expr(f);
hir::ExprKind::Call(f, self.lower_exprs(args))
}
}
ExprKind::MethodCall(box MethodCall { seg, receiver, args, span }) => {
let hir_seg = self.arena.alloc(self.lower_path_segment(
e.span,
seg,
ParamMode::Optional,
ParenthesizedGenericArgs::Err,
ImplTraitContext::Disallowed(ImplTraitPosition::Path),
// Method calls can't have bound modifiers
None,
));
let receiver = self.lower_expr(receiver);
let args =
self.arena.alloc_from_iter(args.iter().map(|x| self.lower_expr_mut(x)));
hir::ExprKind::MethodCall(hir_seg, receiver, args, self.lower_span(*span))
}
ExprKind::Binary(binop, lhs, rhs) => {
let binop = self.lower_binop(*binop);
let lhs = self.lower_expr(lhs);
let rhs = self.lower_expr(rhs);
hir::ExprKind::Binary(binop, lhs, rhs)
}
ExprKind::Unary(op, ohs) => {
let op = self.lower_unop(*op);
let ohs = self.lower_expr(ohs);
hir::ExprKind::Unary(op, ohs)
}
ExprKind::Lit(token_lit) => {
let lit_kind = match LitKind::from_token_lit(*token_lit) {
Ok(lit_kind) => lit_kind,
Err(err) => {
let guar =
report_lit_error(&self.tcx.sess.psess, err, *token_lit, e.span);
LitKind::Err(guar)
}
};
let lit = self.arena.alloc(respan(self.lower_span(e.span), lit_kind));
hir::ExprKind::Lit(lit)
}
ExprKind::IncludedBytes(bytes) => {
let lit = self.arena.alloc(respan(
self.lower_span(e.span),
LitKind::ByteStr(bytes.clone(), StrStyle::Cooked),
));
hir::ExprKind::Lit(lit)
}
ExprKind::Cast(expr, ty) => {
let expr = self.lower_expr(expr);
let ty =
self.lower_ty(ty, ImplTraitContext::Disallowed(ImplTraitPosition::Cast));
hir::ExprKind::Cast(expr, ty)
}
ExprKind::Type(expr, ty) => {
let expr = self.lower_expr(expr);
let ty =
self.lower_ty(ty, ImplTraitContext::Disallowed(ImplTraitPosition::Cast));
hir::ExprKind::Type(expr, ty)
}
ExprKind::AddrOf(k, m, ohs) => {
let ohs = self.lower_expr(ohs);
hir::ExprKind::AddrOf(*k, *m, ohs)
}
ExprKind::Let(pat, scrutinee, span, recovered) => {
hir::ExprKind::Let(self.arena.alloc(hir::LetExpr {
span: self.lower_span(*span),
pat: self.lower_pat(pat),
ty: None,
init: self.lower_expr(scrutinee),
recovered: *recovered,
}))
}
ExprKind::If(cond, then, else_opt) => {
self.lower_expr_if(cond, then, else_opt.as_deref())
}
ExprKind::While(cond, body, opt_label) => self.with_loop_scope(e.id, |this| {
let span = this.mark_span_with_reason(DesugaringKind::WhileLoop, e.span, None);
this.lower_expr_while_in_loop_scope(span, cond, body, *opt_label)
}),
ExprKind::Loop(body, opt_label, span) => self.with_loop_scope(e.id, |this| {
hir::ExprKind::Loop(
this.lower_block(body, false),
this.lower_label(*opt_label),
hir::LoopSource::Loop,
this.lower_span(*span),
)
}),
ExprKind::TryBlock(body) => self.lower_expr_try_block(body),
ExprKind::Match(expr, arms, kind) => hir::ExprKind::Match(
self.lower_expr(expr),
self.arena.alloc_from_iter(arms.iter().map(|x| self.lower_arm(x))),
match kind {
MatchKind::Prefix => hir::MatchSource::Normal,
MatchKind::Postfix => hir::MatchSource::Postfix,
},
),
ExprKind::Await(expr, await_kw_span) => self.lower_expr_await(*await_kw_span, expr),
ExprKind::Closure(box Closure {
binder,
capture_clause,
constness,
coroutine_kind,
movability,
fn_decl,
body,
fn_decl_span,
fn_arg_span,
}) => match coroutine_kind {
Some(coroutine_kind) => self.lower_expr_coroutine_closure(
binder,
*capture_clause,
e.id,
hir_id,
*coroutine_kind,
fn_decl,
body,
*fn_decl_span,
*fn_arg_span,
),
None => self.lower_expr_closure(
binder,
*capture_clause,
e.id,
hir_id,
*constness,
*movability,
fn_decl,
body,
*fn_decl_span,
*fn_arg_span,
),
},
ExprKind::Gen(capture_clause, block, genblock_kind, decl_span) => {
let desugaring_kind = match genblock_kind {
GenBlockKind::Async => hir::CoroutineDesugaring::Async,
GenBlockKind::Gen => hir::CoroutineDesugaring::Gen,
GenBlockKind::AsyncGen => hir::CoroutineDesugaring::AsyncGen,
};
self.make_desugared_coroutine_expr(
*capture_clause,
e.id,
None,
*decl_span,
e.span,
desugaring_kind,
hir::CoroutineSource::Block,
|this| this.with_new_scopes(e.span, |this| this.lower_block_expr(block)),
)
}
ExprKind::Block(blk, opt_label) => {
let opt_label = self.lower_label(*opt_label);
hir::ExprKind::Block(self.lower_block(blk, opt_label.is_some()), opt_label)
}
ExprKind::Assign(el, er, span) => self.lower_expr_assign(el, er, *span, e.span),
ExprKind::AssignOp(op, el, er) => hir::ExprKind::AssignOp(
self.lower_binop(*op),
self.lower_expr(el),
self.lower_expr(er),
),
ExprKind::Field(el, ident) => {
hir::ExprKind::Field(self.lower_expr(el), self.lower_ident(*ident))
}
ExprKind::Index(el, er, brackets_span) => {
hir::ExprKind::Index(self.lower_expr(el), self.lower_expr(er), *brackets_span)
}
ExprKind::Range(Some(e1), Some(e2), RangeLimits::Closed) => {
self.lower_expr_range_closed(e.span, e1, e2)
}
ExprKind::Range(e1, e2, lims) => {
self.lower_expr_range(e.span, e1.as_deref(), e2.as_deref(), *lims)
}
ExprKind::Underscore => {
let guar = self.dcx().emit_err(UnderscoreExprLhsAssign { span: e.span });
hir::ExprKind::Err(guar)
}
ExprKind::Path(qself, path) => {
let qpath = self.lower_qpath(
e.id,
qself,
path,
ParamMode::Optional,
ImplTraitContext::Disallowed(ImplTraitPosition::Path),
None,
);
hir::ExprKind::Path(qpath)
}
ExprKind::Break(opt_label, opt_expr) => {
let opt_expr = opt_expr.as_ref().map(|x| self.lower_expr(x));
hir::ExprKind::Break(self.lower_jump_destination(e.id, *opt_label), opt_expr)
}
ExprKind::Continue(opt_label) => {
hir::ExprKind::Continue(self.lower_jump_destination(e.id, *opt_label))
}
ExprKind::Ret(e) => {
let e = e.as_ref().map(|x| self.lower_expr(x));
hir::ExprKind::Ret(e)
}
ExprKind::Yeet(sub_expr) => self.lower_expr_yeet(e.span, sub_expr.as_deref()),
ExprKind::Become(sub_expr) => {
let sub_expr = self.lower_expr(sub_expr);
hir::ExprKind::Become(sub_expr)
}
ExprKind::InlineAsm(asm) => {
hir::ExprKind::InlineAsm(self.lower_inline_asm(e.span, asm))
}
ExprKind::FormatArgs(fmt) => self.lower_format_args(e.span, fmt),
ExprKind::OffsetOf(container, fields) => hir::ExprKind::OffsetOf(
self.lower_ty(
container,
ImplTraitContext::Disallowed(ImplTraitPosition::OffsetOf),
),
self.arena.alloc_from_iter(fields.iter().map(|&ident| self.lower_ident(ident))),
),
ExprKind::Struct(se) => {
let rest = match &se.rest {
StructRest::Base(e) => Some(self.lower_expr(e)),
StructRest::Rest(sp) => {
let guar = self.dcx().emit_err(BaseExpressionDoubleDot { span: *sp });
Some(&*self.arena.alloc(self.expr_err(*sp, guar)))
}
StructRest::None => None,
};
hir::ExprKind::Struct(
self.arena.alloc(self.lower_qpath(
e.id,
&se.qself,
&se.path,
ParamMode::Optional,
ImplTraitContext::Disallowed(ImplTraitPosition::Path),
None,
)),
self.arena
.alloc_from_iter(se.fields.iter().map(|x| self.lower_expr_field(x))),
rest,
)
}
ExprKind::Yield(opt_expr) => self.lower_expr_yield(e.span, opt_expr.as_deref()),
ExprKind::Err(guar) => hir::ExprKind::Err(*guar),
ExprKind::Dummy => {
span_bug!(e.span, "lowered ExprKind::Dummy")
}
ExprKind::Try(sub_expr) => self.lower_expr_try(e.span, sub_expr),
ExprKind::Paren(_) | ExprKind::ForLoop { .. } => {
unreachable!("already handled")
}
ExprKind::MacCall(_) => panic!("{:?} shouldn't exist here", e.span),
};
hir::Expr { hir_id, kind, span: self.lower_span(e.span) }
})
}
fn lower_unop(&mut self, u: UnOp) -> hir::UnOp {
match u {
UnOp::Deref => hir::UnOp::Deref,
UnOp::Not => hir::UnOp::Not,
UnOp::Neg => hir::UnOp::Neg,
}
}
fn lower_binop(&mut self, b: BinOp) -> BinOp {
Spanned { node: b.node, span: self.lower_span(b.span) }
}
fn lower_legacy_const_generics(
&mut self,
mut f: Expr,
args: ThinVec<AstP<Expr>>,
legacy_args_idx: &[usize],
) -> hir::ExprKind<'hir> {
let ExprKind::Path(None, path) = &mut f.kind else {
unreachable!();
};
// Split the arguments into const generics and normal arguments
let mut real_args = vec![];
let mut generic_args = ThinVec::new();
for (idx, arg) in args.into_iter().enumerate() {
if legacy_args_idx.contains(&idx) {
let parent_def_id = self.current_hir_id_owner;
let node_id = self.next_node_id();
// Add a definition for the in-band const def.
self.create_def(
parent_def_id.def_id,
node_id,
kw::Empty,
DefKind::AnonConst,
f.span,
);
let anon_const = AnonConst { id: node_id, value: arg };
generic_args.push(AngleBracketedArg::Arg(GenericArg::Const(anon_const)));
} else {
real_args.push(arg);
}
}
// Add generic args to the last element of the path.
let last_segment = path.segments.last_mut().unwrap();
assert!(last_segment.args.is_none());
last_segment.args = Some(AstP(GenericArgs::AngleBracketed(AngleBracketedArgs {
span: DUMMY_SP,
args: generic_args,
})));
// Now lower everything as normal.
let f = self.lower_expr(&f);
hir::ExprKind::Call(f, self.lower_exprs(&real_args))
}
fn lower_expr_if(
&mut self,
cond: &Expr,
then: &Block,
else_opt: Option<&Expr>,
) -> hir::ExprKind<'hir> {
let lowered_cond = self.lower_cond(cond);
let then_expr = self.lower_block_expr(then);
if let Some(rslt) = else_opt {
hir::ExprKind::If(
lowered_cond,
self.arena.alloc(then_expr),
Some(self.lower_expr(rslt)),
)
} else {
hir::ExprKind::If(lowered_cond, self.arena.alloc(then_expr), None)
}
}
// Lowers a condition (i.e. `cond` in `if cond` or `while cond`), wrapping it in a terminating scope
// so that temporaries created in the condition don't live beyond it.
fn lower_cond(&mut self, cond: &Expr) -> &'hir hir::Expr<'hir> {
fn has_let_expr(expr: &Expr) -> bool {
match &expr.kind {
ExprKind::Binary(_, lhs, rhs) => has_let_expr(lhs) || has_let_expr(rhs),
ExprKind::Let(..) => true,
_ => false,
}
}
// We have to take special care for `let` exprs in the condition, e.g. in
// `if let pat = val` or `if foo && let pat = val`, as we _do_ want `val` to live beyond the
// condition in this case.
//
// In order to maintain the drop behavior for the non `let` parts of the condition,
// we still wrap them in terminating scopes, e.g. `if foo && let pat = val` essentially
// gets transformed into `if { let _t = foo; _t } && let pat = val`
match &cond.kind {
ExprKind::Binary(op @ Spanned { node: ast::BinOpKind::And, .. }, lhs, rhs)
if has_let_expr(cond) =>
{
let op = self.lower_binop(*op);
let lhs = self.lower_cond(lhs);
let rhs = self.lower_cond(rhs);
self.arena.alloc(self.expr(cond.span, hir::ExprKind::Binary(op, lhs, rhs)))
}
ExprKind::Let(..) => self.lower_expr(cond),
_ => {
let cond = self.lower_expr(cond);
let reason = DesugaringKind::CondTemporary;
let span_block = self.mark_span_with_reason(reason, cond.span, None);
self.expr_drop_temps(span_block, cond)
}
}
}
// We desugar: `'label: while $cond $body` into:
//
// ```
// 'label: loop {
// if { let _t = $cond; _t } {
// $body
// }
// else {
// break;
// }
// }
// ```
//
// Wrap in a construct equivalent to `{ let _t = $cond; _t }`
// to preserve drop semantics since `while $cond { ... }` does not
// let temporaries live outside of `cond`.
fn lower_expr_while_in_loop_scope(
&mut self,
span: Span,
cond: &Expr,
body: &Block,
opt_label: Option<Label>,
) -> hir::ExprKind<'hir> {
let lowered_cond = self.with_loop_condition_scope(|t| t.lower_cond(cond));
let then = self.lower_block_expr(body);
let expr_break = self.expr_break(span);
let stmt_break = self.stmt_expr(span, expr_break);
let else_blk = self.block_all(span, arena_vec![self; stmt_break], None);
let else_expr = self.arena.alloc(self.expr_block(else_blk));
let if_kind = hir::ExprKind::If(lowered_cond, self.arena.alloc(then), Some(else_expr));
let if_expr = self.expr(span, if_kind);
let block = self.block_expr(self.arena.alloc(if_expr));
let span = self.lower_span(span.with_hi(cond.span.hi()));
let opt_label = self.lower_label(opt_label);
hir::ExprKind::Loop(block, opt_label, hir::LoopSource::While, span)
}
/// Desugar `try { <stmts>; <expr> }` into `{ <stmts>; ::std::ops::Try::from_output(<expr>) }`,
/// `try { <stmts>; }` into `{ <stmts>; ::std::ops::Try::from_output(()) }`
/// and save the block id to use it as a break target for desugaring of the `?` operator.
fn lower_expr_try_block(&mut self, body: &Block) -> hir::ExprKind<'hir> {
self.with_catch_scope(body.id, |this| {
let mut block = this.lower_block_noalloc(body, true);
// Final expression of the block (if present) or `()` with span at the end of block
let (try_span, tail_expr) = if let Some(expr) = block.expr.take() {
(
this.mark_span_with_reason(
DesugaringKind::TryBlock,
expr.span,
Some(this.allow_try_trait.clone()),
),
expr,
)
} else {
let try_span = this.mark_span_with_reason(
DesugaringKind::TryBlock,
this.tcx.sess.source_map().end_point(body.span),
Some(this.allow_try_trait.clone()),
);
(try_span, this.expr_unit(try_span))
};
let ok_wrapped_span =
this.mark_span_with_reason(DesugaringKind::TryBlock, tail_expr.span, None);
// `::std::ops::Try::from_output($tail_expr)`
block.expr = Some(this.wrap_in_try_constructor(
hir::LangItem::TryTraitFromOutput,
try_span,
tail_expr,
ok_wrapped_span,
));
hir::ExprKind::Block(this.arena.alloc(block), None)
})
}
fn wrap_in_try_constructor(
&mut self,
lang_item: hir::LangItem,
method_span: Span,
expr: &'hir hir::Expr<'hir>,
overall_span: Span,
) -> &'hir hir::Expr<'hir> {
let constructor = self.arena.alloc(self.expr_lang_item_path(method_span, lang_item));
self.expr_call(overall_span, constructor, std::slice::from_ref(expr))
}
fn lower_arm(&mut self, arm: &Arm) -> hir::Arm<'hir> {
let pat = self.lower_pat(&arm.pat);
let guard = arm.guard.as_ref().map(|cond| self.lower_expr(cond));
let hir_id = self.next_id();
let span = self.lower_span(arm.span);
self.lower_attrs(hir_id, &arm.attrs);
let is_never_pattern = pat.is_never_pattern();
let body = if let Some(body) = &arm.body
&& !is_never_pattern
{
self.lower_expr(body)
} else {
// Either `body.is_none()` or `is_never_pattern` here.
if !is_never_pattern {
if self.tcx.features().never_patterns {
// If the feature is off we already emitted the error after parsing.
let suggestion = span.shrink_to_hi();
self.dcx().emit_err(MatchArmWithNoBody { span, suggestion });
}
} else if let Some(body) = &arm.body {
self.dcx().emit_err(NeverPatternWithBody { span: body.span });
} else if let Some(g) = &arm.guard {
self.dcx().emit_err(NeverPatternWithGuard { span: g.span });
}
// We add a fake `loop {}` arm body so that it typecks to `!`. The mir lowering of never
// patterns ensures this loop is not reachable.
let block = self.arena.alloc(hir::Block {
stmts: &[],
expr: None,
hir_id: self.next_id(),
rules: hir::BlockCheckMode::DefaultBlock,
span,
targeted_by_break: false,
});
self.arena.alloc(hir::Expr {
hir_id: self.next_id(),
kind: hir::ExprKind::Loop(block, None, hir::LoopSource::Loop, span),
span,
})
};
hir::Arm { hir_id, pat, guard, body, span }
}
/// Lower/desugar a coroutine construct.
///
/// In particular, this creates the correct async resume argument and `_task_context`.
///
/// This results in:
///
/// ```text
/// static move? |<_task_context?>| -> <return_ty> {
/// <body>
/// }
/// ```
pub(super) fn make_desugared_coroutine_expr(
&mut self,
capture_clause: CaptureBy,
closure_node_id: NodeId,
return_ty: Option<hir::FnRetTy<'hir>>,
fn_decl_span: Span,
span: Span,
desugaring_kind: hir::CoroutineDesugaring,
coroutine_source: hir::CoroutineSource,
body: impl FnOnce(&mut Self) -> hir::Expr<'hir>,
) -> hir::ExprKind<'hir> {
let coroutine_kind = hir::CoroutineKind::Desugared(desugaring_kind, coroutine_source);
// The `async` desugaring takes a resume argument and maintains a `task_context`,
// whereas a generator does not.
let (inputs, params, task_context): (&[_], &[_], _) = match desugaring_kind {
hir::CoroutineDesugaring::Async | hir::CoroutineDesugaring::AsyncGen => {
// Resume argument type: `ResumeTy`
let unstable_span = self.mark_span_with_reason(
DesugaringKind::Async,
self.lower_span(span),
Some(self.allow_gen_future.clone()),
);
let resume_ty = self.make_lang_item_qpath(hir::LangItem::ResumeTy, unstable_span);
let input_ty = hir::Ty {
hir_id: self.next_id(),
kind: hir::TyKind::Path(resume_ty),
span: unstable_span,
};
let inputs = arena_vec![self; input_ty];
// Lower the argument pattern/ident. The ident is used again in the `.await` lowering.
let (pat, task_context_hid) = self.pat_ident_binding_mode(
span,
Ident::with_dummy_span(sym::_task_context),
hir::BindingMode::MUT,
);
let param = hir::Param {
hir_id: self.next_id(),
pat,
ty_span: self.lower_span(span),
span: self.lower_span(span),
};
let params = arena_vec![self; param];
(inputs, params, Some(task_context_hid))
}
hir::CoroutineDesugaring::Gen => (&[], &[], None),
};
let output =
return_ty.unwrap_or_else(|| hir::FnRetTy::DefaultReturn(self.lower_span(span)));
let fn_decl = self.arena.alloc(hir::FnDecl {
inputs,
output,
c_variadic: false,
implicit_self: hir::ImplicitSelfKind::None,
lifetime_elision_allowed: false,
});
let body = self.lower_body(move |this| {
this.coroutine_kind = Some(coroutine_kind);
let old_ctx = this.task_context;
if task_context.is_some() {
this.task_context = task_context;
}
let res = body(this);
this.task_context = old_ctx;
(params, res)
});
// `static |<_task_context?>| -> <return_ty> { <body> }`:
hir::ExprKind::Closure(self.arena.alloc(hir::Closure {
def_id: self.local_def_id(closure_node_id),
binder: hir::ClosureBinder::Default,
capture_clause,
bound_generic_params: &[],
fn_decl,
body,
fn_decl_span: self.lower_span(fn_decl_span),
fn_arg_span: None,
kind: hir::ClosureKind::Coroutine(coroutine_kind),
constness: hir::Constness::NotConst,
}))
}
/// Forwards a possible `#[track_caller]` annotation from `outer_hir_id` to
/// `inner_hir_id` in case the `async_fn_track_caller` feature is enabled.
pub(super) fn maybe_forward_track_caller(
&mut self,
span: Span,
outer_hir_id: HirId,
inner_hir_id: HirId,
) {
if self.tcx.features().async_fn_track_caller
&& let Some(attrs) = self.attrs.get(&outer_hir_id.local_id)
&& attrs.into_iter().any(|attr| attr.has_name(sym::track_caller))
{
let unstable_span = self.mark_span_with_reason(
DesugaringKind::Async,
span,
Some(self.allow_gen_future.clone()),
);
self.lower_attrs(
inner_hir_id,
&[Attribute {
kind: AttrKind::Normal(ptr::P(NormalAttr::from_ident(Ident::new(
sym::track_caller,
span,
)))),
id: self.tcx.sess.psess.attr_id_generator.mk_attr_id(),
style: AttrStyle::Outer,
span: unstable_span,
}],
);
}
}
/// Desugar `<expr>.await` into:
/// ```ignore (pseudo-rust)
/// match ::std::future::IntoFuture::into_future(<expr>) {
/// mut __awaitee => loop {
/// match unsafe { ::std::future::Future::poll(
/// <::std::pin::Pin>::new_unchecked(&mut __awaitee),
/// ::std::future::get_context(task_context),
/// ) } {
/// ::std::task::Poll::Ready(result) => break result,
/// ::std::task::Poll::Pending => {}
/// }
/// task_context = yield ();
/// }
/// }
/// ```
fn lower_expr_await(&mut self, await_kw_span: Span, expr: &Expr) -> hir::ExprKind<'hir> {
let expr = self.arena.alloc(self.lower_expr_mut(expr));
self.make_lowered_await(await_kw_span, expr, FutureKind::Future)
}
/// Takes an expr that has already been lowered and generates a desugared await loop around it
fn make_lowered_await(
&mut self,
await_kw_span: Span,
expr: &'hir hir::Expr<'hir>,
await_kind: FutureKind,
) -> hir::ExprKind<'hir> {
let full_span = expr.span.to(await_kw_span);
let is_async_gen = match self.coroutine_kind {
Some(hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Async, _)) => false,
Some(hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::AsyncGen, _)) => true,
Some(hir::CoroutineKind::Coroutine(_))
| Some(hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Gen, _))
| None => {
// Lower to a block `{ EXPR; <error> }` so that the awaited expr
// is not accidentally orphaned.
let stmt_id = self.next_id();
let expr_err = self.expr(
expr.span,
hir::ExprKind::Err(self.dcx().emit_err(AwaitOnlyInAsyncFnAndBlocks {
await_kw_span,
item_span: self.current_item,
})),
);
return hir::ExprKind::Block(
self.block_all(
expr.span,
arena_vec![self; hir::Stmt {
hir_id: stmt_id,
kind: hir::StmtKind::Semi(expr),
span: expr.span,
}],
Some(self.arena.alloc(expr_err)),
),
None,
);
}
};
let features = match await_kind {
FutureKind::Future => None,
FutureKind::AsyncIterator => Some(self.allow_for_await.clone()),
};
let span = self.mark_span_with_reason(DesugaringKind::Await, await_kw_span, features);
let gen_future_span = self.mark_span_with_reason(
DesugaringKind::Await,
full_span,
Some(self.allow_gen_future.clone()),
);
let expr_hir_id = expr.hir_id;
// Note that the name of this binding must not be changed to something else because
// debuggers and debugger extensions expect it to be called `__awaitee`. They use
// this name to identify what is being awaited by a suspended async functions.
let awaitee_ident = Ident::with_dummy_span(sym::__awaitee);
let (awaitee_pat, awaitee_pat_hid) =
self.pat_ident_binding_mode(gen_future_span, awaitee_ident, hir::BindingMode::MUT);
let task_context_ident = Ident::with_dummy_span(sym::_task_context);
// unsafe {
// ::std::future::Future::poll(
// ::std::pin::Pin::new_unchecked(&mut __awaitee),
// ::std::future::get_context(task_context),
// )
// }
let poll_expr = {
let awaitee = self.expr_ident(span, awaitee_ident, awaitee_pat_hid);
let ref_mut_awaitee = self.expr_mut_addr_of(span, awaitee);
let Some(task_context_hid) = self.task_context else {
unreachable!("use of `await` outside of an async context.");
};
let task_context = self.expr_ident_mut(span, task_context_ident, task_context_hid);
let new_unchecked = self.expr_call_lang_item_fn_mut(
span,
hir::LangItem::PinNewUnchecked,
arena_vec![self; ref_mut_awaitee],
);
let get_context = self.expr_call_lang_item_fn_mut(
gen_future_span,
hir::LangItem::GetContext,
arena_vec![self; task_context],
);
let call = match await_kind {
FutureKind::Future => self.expr_call_lang_item_fn(
span,
hir::LangItem::FuturePoll,
arena_vec![self; new_unchecked, get_context],
),
FutureKind::AsyncIterator => self.expr_call_lang_item_fn(
span,
hir::LangItem::AsyncIteratorPollNext,
arena_vec![self; new_unchecked, get_context],
),
};
self.arena.alloc(self.expr_unsafe(call))
};
// `::std::task::Poll::Ready(result) => break result`
let loop_node_id = self.next_node_id();
let loop_hir_id = self.lower_node_id(loop_node_id);
let ready_arm = {
let x_ident = Ident::with_dummy_span(sym::result);
let (x_pat, x_pat_hid) = self.pat_ident(gen_future_span, x_ident);
let x_expr = self.expr_ident(gen_future_span, x_ident, x_pat_hid);
let ready_field = self.single_pat_field(gen_future_span, x_pat);
let ready_pat = self.pat_lang_item_variant(span, hir::LangItem::PollReady, ready_field);
let break_x = self.with_loop_scope(loop_node_id, move |this| {
let expr_break =
hir::ExprKind::Break(this.lower_loop_destination(None), Some(x_expr));
this.arena.alloc(this.expr(gen_future_span, expr_break))
});
self.arm(ready_pat, break_x)
};
// `::std::task::Poll::Pending => {}`
let pending_arm = {
let pending_pat = self.pat_lang_item_variant(span, hir::LangItem::PollPending, &[]);
let empty_block = self.expr_block_empty(span);
self.arm(pending_pat, empty_block)
};
let inner_match_stmt = {
let match_expr = self.expr_match(
span,
poll_expr,
arena_vec![self; ready_arm, pending_arm],
hir::MatchSource::AwaitDesugar,
);
self.stmt_expr(span, match_expr)
};
// Depending on `async` of `async gen`:
// async - task_context = yield ();
// async gen - task_context = yield ASYNC_GEN_PENDING;
let yield_stmt = {
let yielded = if is_async_gen {
self.arena.alloc(self.expr_lang_item_path(span, hir::LangItem::AsyncGenPending))
} else {
self.expr_unit(span)
};
let yield_expr = self.expr(
span,
hir::ExprKind::Yield(yielded, hir::YieldSource::Await { expr: Some(expr_hir_id) }),
);
let yield_expr = self.arena.alloc(yield_expr);
let Some(task_context_hid) = self.task_context else {
unreachable!("use of `await` outside of an async context.");
};
let lhs = self.expr_ident(span, task_context_ident, task_context_hid);
let assign =
self.expr(span, hir::ExprKind::Assign(lhs, yield_expr, self.lower_span(span)));
self.stmt_expr(span, assign)
};
let loop_block = self.block_all(span, arena_vec![self; inner_match_stmt, yield_stmt], None);
// loop { .. }
let loop_expr = self.arena.alloc(hir::Expr {
hir_id: loop_hir_id,
kind: hir::ExprKind::Loop(
loop_block,
None,
hir::LoopSource::Loop,
self.lower_span(span),
),
span: self.lower_span(span),
});
// mut __awaitee => loop { ... }
let awaitee_arm = self.arm(awaitee_pat, loop_expr);
// `match ::std::future::IntoFuture::into_future(<expr>) { ... }`
let into_future_expr = match await_kind {
FutureKind::Future => self.expr_call_lang_item_fn(
span,
hir::LangItem::IntoFutureIntoFuture,
arena_vec![self; *expr],
),
// Not needed for `for await` because we expect to have already called
// `IntoAsyncIterator::into_async_iter` on it.
FutureKind::AsyncIterator => expr,
};
// match <into_future_expr> {
// mut __awaitee => loop { .. }
// }
hir::ExprKind::Match(
into_future_expr,
arena_vec![self; awaitee_arm],
hir::MatchSource::AwaitDesugar,
)
}
fn lower_expr_closure(
&mut self,
binder: &ClosureBinder,
capture_clause: CaptureBy,
closure_id: NodeId,
closure_hir_id: hir::HirId,
constness: Const,
movability: Movability,
decl: &FnDecl,
body: &Expr,
fn_decl_span: Span,
fn_arg_span: Span,
) -> hir::ExprKind<'hir> {
let (binder_clause, generic_params) = self.lower_closure_binder(binder);
let (body_id, closure_kind) = self.with_new_scopes(fn_decl_span, move |this| {
let mut coroutine_kind = if this
.attrs
.get(&closure_hir_id.local_id)
.is_some_and(|attrs| attrs.iter().any(|attr| attr.has_name(sym::coroutine)))
{
Some(hir::CoroutineKind::Coroutine(Movability::Movable))
} else {
None
};
let body_id = this.lower_fn_body(decl, |this| {
this.coroutine_kind = coroutine_kind;
let e = this.lower_expr_mut(body);
coroutine_kind = this.coroutine_kind;
e
});
let coroutine_option =
this.closure_movability_for_fn(decl, fn_decl_span, coroutine_kind, movability);
(body_id, coroutine_option)
});
let bound_generic_params = self.lower_lifetime_binder(closure_id, generic_params);
// Lower outside new scope to preserve `is_in_loop_condition`.
let fn_decl = self.lower_fn_decl(decl, closure_id, fn_decl_span, FnDeclKind::Closure, None);
let c = self.arena.alloc(hir::Closure {
def_id: self.local_def_id(closure_id),
binder: binder_clause,
capture_clause,
bound_generic_params,